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Suppose you stand with one foot on ceramic flooring and one foot on a wool carpet, making contact over an area of 80 . 0 cm 2 with each foot. Both the ceramic and the carpet are 2.00 cm thick and are 10. C on their bottom sides. At what rate must heat transfer occur from each foot to keep the top of the ceramic and carpet at 33 . C ?

A man consumes 3000 kcal of food in one day, converting most of it to maintain body temperature. If he loses half this energy by evaporating water (through breathing and sweating), how many kilograms of water evaporate?

2.59 kg

(a) A firewalker runs across a bed of hot coals without sustaining burns. Calculate the heat transferred by conduction into the sole of one foot of a firewalker given that the bottom of the foot is a 3.00-mm-thick callus with a conductivity at the low end of the range for wood and its density is 300  kg/m 3 size 12{"300"`"kg/m" rSup { size 8{3} } } {} . The area of contact is 25 . 0  cm 2 size 12{"25" "." 0`"cm" rSup { size 8{2} } } {} , the temperature of the coals is 700º C size 12{"700"°C} {} , and the time in contact is 1.00 s.

(b) What temperature increase is produced in the 25 . 0  cm 3 size 12{"25" "." 0`"cm" rSup { size 8{3} } } {} of tissue affected?

(c) What effect do you think this will have on the tissue, keeping in mind that a callus is made of dead cells?

(a) What is the rate of heat conduction through the 3.00-cm-thick fur of a large animal having a 1 . 40-m 2 size 12{1 "." "40-m" rSup { size 8{2} } } {} surface area? Assume that the animal’s skin temperature is 32 . C , that the air temperature is 5 . 00º C size 12{ - 5 "." "00"°C} {} , and that fur has the same thermal conductivity as air. (b) What food intake will the animal need in one day to replace this heat transfer?

(a) 39.7 W

(b) 820 kcal

A walrus transfers energy by conduction through its blubber at the rate of 150 W when immersed in 1 .00ºC water. The walrus’s internal core temperature is 37. C size 12{"37" "." 0°C} {} , and it has a surface area of 2 .00 m 2 . What is the average thickness of its blubber, which has the conductivity of fatty tissues without blood?

The figure shows a walrus on an ice bank near the water. The tusks the walrus are visible.
Walrus on ice. (credit: Captain Budd Christman, NOAA Corps)

Compare the rate of heat conduction through a 13.0-cm-thick wall that has an area of 10 . 0  m 2 size 12{"10" "." 0`m rSup { size 8{2} } } {} and a thermal conductivity twice that of glass wool with the rate of heat conduction through a window that is 0.750 cm thick and that has an area of 2 . 00  m 2 size 12{2 "." "00"`m rSup { size 8{2} } } {} , assuming the same temperature difference across each.

35 to 1, window to wall

Suppose a person is covered head to foot by wool clothing with average thickness of 2.00 cm and is transferring energy by conduction through the clothing at the rate of 50.0 W. What is the temperature difference across the clothing, given the surface area is 1 . 40  m 2 size 12{1 "." "40"`m rSup { size 8{2} } } {} ?

Some stove tops are smooth ceramic for easy cleaning. If the ceramic is 0.600 cm thick and heat conduction occurs through the same area and at the same rate as computed in [link] , what is the temperature difference across it? Ceramic has the same thermal conductivity as glass and brick.

1 . 05 × 10 3 K size 12{1 "." "05" times "10" rSup { size 8{3} } `K} {}

One easy way to reduce heating (and cooling) costs is to add extra insulation in the attic of a house. Suppose the house already had 15 cm of fiberglass insulation in the attic and in all the exterior surfaces. If you added an extra 8.0 cm of fiberglass to the attic, then by what percentage would the heating cost of the house drop? Take the single story house to be of dimensions 10 m by 15 m by 3.0 m. Ignore air infiltration and heat loss through windows and doors.

(a) Calculate the rate of heat conduction through a double-paned window that has a 1 . 50 -m 2 area and is made of two panes of 0.800-cm-thick glass separated by a 1.00-cm air gap. The inside surface temperature is 15 . C size 12{"15" "." 0°C} {} , while that on the outside is 10 . C size 12{ - "10" "." 0°C} {} . (Hint: There are identical temperature drops across the two glass panes. First find these and then the temperature drop across the air gap. This problem ignores the increased heat transfer in the air gap due to convection.)

(b) Calculate the rate of heat conduction through a 1.60-cm-thick window of the same area and with the same temperatures. Compare your answer with that for part (a).

(a) 83 W

(b) 24 times that of a double pane window.

Many decisions are made on the basis of the payback period: the time it will take through savings to equal the capital cost of an investment. Acceptable payback times depend upon the business or philosophy one has. (For some industries, a payback period is as small as two years.) Suppose you wish to install the extra insulation in [link] . If energy cost $1.00 per million joules and the insulation was $4.00 per square meter, then calculate the simple payback time. Take the average Δ T for the 120 day heating season to be 15. C .

For the human body, what is the rate of heat transfer by conduction through the body’s tissue with the following conditions: the tissue thickness is 3.00 cm, the change in temperature is 2 . 00º C size 12{2 "." "00"°C} {} , and the skin area is 1 . 50  m 2 size 12{1 "." "50"`m rSup { size 8{2} } } {} . How does this compare with the average heat transfer rate to the body resulting from an energy intake of about 2400 kcal per day? (No exercise is included.)

20.0 W, 17.2% of 2400 kcal per day

Questions & Answers

Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, College physics ii. OpenStax CNX. Nov 29, 2012 Download for free at http://legacy.cnx.org/content/col11458/1.2
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